We intend to run a two week course jointly funded by NATO, NIH, FEBS and the pharmaceutical industry. We have invited 16 eminent scientists (see list herewith enclosed) to review the present knowledge on the medically important virus classes and the antiviral compounds which are presently available, in an attempt to define possible targets for future drug design. Other leading scientists will be invited to give research seminars which will cover in detail the present state of the art in selected areas. There will be an opportunity for younger scientists to present posters describing their work and tutorial sessions will be arranged as required. As a result of a NATO Course organized 3 years ago, 7-18 May 1979 in Sogesta (Italy), several collaborative projects have been started between scientists from different disciplines, and in view of the advances in the knowledge of the molecular biology of viruses and the advances in antiviral chemotherapy we have decided to organize a sequel to this previous Course. The advantage of such Course is its duration (2 weeks), the interdisciplinary nature of the participants and the way in which review lectures, research seminars, posters and tutorials can all be accommodated to suit the occasion. Thus the aim of the Course is to emphasize the interdisciplinary nature of this area of research, to enable the senior scientists in one discipline to learn from similar people in another related and relevant discipline so that collaborative projects can be started on a basis of mutual understanding. Also the Course will present an opportunity to younger scientists who have just entered the field to assimilate current knowledge and make personal contacts which foster their research career. Although primarily aimed at the chemotherapy of virus infections, the Course also has considerable implications for several other fields such as cancer and transplantation, i.e. in the treatment of life-threatening virus infections in immunosuppressed patients.